Teleconferencing services that allow participants from multiple locations to confer with each other over the wireline telecommunications network are well known. With such services, a number of participants can communicate with each other by telephone and participate in a conference as if they were in the same location. As in any "real" single-site conference, the number of participants in a teleconference can range between very few to quite a large number, such as several hundred, or even higher.
A teleconferencing bridge is a software controlled piece of hardware that is used to combine signals from multiple participants that are inputted to its multiple ports over telephone circuits. The bridge then outputs, at each of its ports, a single combined signal that is transmitted over the telephone circuits back to each participant. Obviously, if the voice signals from too many simultaneously talking participants are combined, the signal returned to each conference participant will be unintelligible. Thus, in order to prevent such a gibberish signal from being transmitted back to each participant, the teleconferencing bridge combines only a selected few of the incoming signals for output and return to each participant. Selection of which plural input signals are combined is generally performed by the teleconferencing bridge based on a measurable predetermined signal characteristic, such as signal power. For example, the bridge, measures the power of each of its input signals, selects a predetermined number (for example, three) of those having the highest power, combines these three signals into a single signal, and returns the combined signal to each participant over the wireline teleconununications network. As the conference progresses, different participant's signals are selected, combined and returned. Thus, the bridge dynamically changes the constituent signals of the combined signal that is returned to each conference participant.
A teleconferencing bridge performs the aforedescribed functions of measuring the predetermined characteristic of the signal on each input circuit from the wireline network, such as signal power, selecting a predetermined number of the signals having the highest power, combining those selected predetermined number of signals, and bridging the combined signal back to each wireline circuit. Such teleconferencing bridges currently exist, can be located anywhere, and can handle conferences having a large number of participants. Furthermore, those ports of the bridge that are not being used for one conference can handle the bridging functions for other conferences.
Generally, a teleconferencing bridge is software controlled through a control system, which is responsive to an operator input. A conference operator obtains from the conference organizer information such as the time and date of the conference, the expected duration of the conference, and the number of participants. A specific physical bridge is then reserved for the specified time, date and duration, together with the number of ports on the bridge necessary to support the maximum number of conference participants. Codes are assigned for the conference host and for the conference participants allowing them access to the bridge. During the reserved conference time, the control system configures the allocated ports together and permits access to the bridge by the host and the participants. As previously described, the bridge combines the predetermined number of strongest input signals into a single output signal, which is outputted on each port to each participant. That predetermined number is generally preset at the bridge. Also, during the conference the control system tracks usage of the bridge for billing purposes.
FIG. 1 shows a prior art teleconferencing configuration in which multiple participants are located around the country but concentrated in groups in the geographic areas of New York, Dallas, and San Francisco. Participants 101-1-101-N.sub.1 are located in various locations throughout the New York area, participants 102-1-102-N.sub.2 are located in various locations throughout the Dallas area, and participants 103-1-103-N.sub.3 are located in various locations throughout the San Francisco area. There is thus a total of N.sub.1 +N.sub.2 +N.sub.3 conference participants. The telecommunications device, such as a telephone, associated with each New York participant is connected to the interexchange wireline network 106 through an associated local exchange switch (LES) 104-k (k=1, 2, . . . ). Participants 101-1 and 101-2 are shown located within the same local exchange and are thus associated with the same local exchange switch 104-1. Each New York local exchange switch 104-k (k=1, 2, . . . ) is connected to an interexchange switch 105, such as a 4ESS.RTM. switch, manufactured by AT&T Corp., which is connected to the wireline interexchange network 106. The telecommunications device of each San Francisco participant is similarly connected through associated local exchange company switches 107-k (k=1, 2, . . . ), and through interexchange switch 108, to the wireline interexchange network 106. The telecommunications device of each Dallas participant is directly connected to the interexchange network 106 through interexchange switch 109, bypassing the local exchange network.
The interexchange switches 105, 109, and 108 thus connect N.sub.1, N.sub.2, and N.sub.3 circuits, respectively, to the wireline interexchange network 106. These N.sub.1 +N.sub.2 +N.sub.3 long distance circuits are connected through the network 106 to the interexchange switch 110 associated with the particular teleconference bridge hardware 111 which has been reserved for the conference and which is located in a different geographic area. As shown in FIG. 1, the N.sub.1 +N.sub.2 +N.sub.3 output circuits (telephone lines) 120 of switch 110 are directly connected to the particular N.sub.1 +N.sub.2 +N.sub.3 ports of bridge 111 that have been reserved for the conference. If bridge 111 is not directly associated with and directly connected to an interexchange switch 110, circuits 120 would be connected to a local exchange switch (not shown) and thence to bridge 111.
As previously described, a control system 112, after earlier communication over a data network 113 with the conference arranger 114, configures the bridge 111 by specifying the particular N.sub.1 +N.sub.2 +N.sub.3 ports for use by the conference. As noted hereinabove but not shown in FIG. 1, bridge 111 can simultaneously handle other conferences on any of its other available ports. Bridge 111 selects from among the N.sub.1 +N.sub.2 +N.sub.3 input signals present at its specified N.sub.1 +N.sub.2 +N.sub.3 ports, the N signals (for example, three) having the highest power. These three selected signals are combined into a single signal, which is returned on each of the circuits 120 to interexchange switch 110 for transmission through the interexchange network 106 back to the telecommunications device of each New York, Dallas, and San Francisco conference participant. Bridge 111 constantly changes the three selected signals bridged to the telecommunications device associated with each participant in accordance with the dynamics of the signals transmitted by all the conference participants' devices.
As can be noted in FIG. 1, a total of N.sub.1 +N.sub.2 +N.sub.3 two-way interexchange circuits are required to support the single conference during which, at any instant, only three different participant's signals are combined and returned to all the participants. When N.sub.1, N.sub.2 and N.sub.3 are large numbers, which is often the case in large teleconferencing situations, a highly inefficient use is made of the interexchange facilities.